The court of second instance hears the case within the limits of the appeal, but within the limits of the appeal it takes into account ex officio the invalidity of the proceedings.
Within the limits of the appeal, the court of second instance may ex officio hear the case also for the benefit of co-participants who have not appealed against the judgment, if the rights or obligations that are the subject of the appeal are common to them.
These co-participants must be notified of the hearing; they may submit preparatory letters It is inadmissible to consider in appeal proceedings claims against separate entities acting in the lawsuit on the defendant's side, in respect of which the claims were dismissed in the judgment of the first instance court and the plaintiff did not appeal against this decision (III PK 7/2004).